Acetylene process



March 27, 1956 J. BILLS ACETYLENE PROCESS Filed April 21, 1952 M Wm 4\hm MAM a a, 4 w w w Jill/F474! United States Patent ACETYLENE PRUCESSJohn L. Bills, Long Beach, Calif., assignor to Union Oil Company ofCalifornia, Los Angeles, Calif., a corporation of California ApplicationApril 21, 1952, Serial No. 283,269

Claims. (Cl. 26tl679) This invention relates to methods and means forthe production of acetylene and other unsaturated hydrocarbons by thethermal cracking of hydrocarbon gases. More specifically it is concernedwith cracking methods employingla solid, particle-form heat-transfermedium to supply the thermal requirements of the reaction. The essentialfeatures of novelty reside in contacting the solids and gases in suchmanner as to minimize gas/solids velocity difierentials, and also inmaintaining optimum temperatures, pressures and reaction times, wherebymaximum yields are obtained, and coking .is minimized.

The thermal cracking of hydrocarbon gases at high temperatures .to formacetylene and other unsaturated hydrocarbons has been heretoforeproposed, as for example, by passing the feed gases through a heatedtube. However, such processes, as previously practiced, are found toresult in excessive coke formation on the Walls of the reactor whichobstructs gas flow and inhibits effective heat transfer through thereactor walls. Considerable difiiculty is therefore usually encounteredin con-- trolling reaction gas temperatures, flow rates and reactiontime. In order to overcome some of these difiiculties it has recentlybeen proposed to employ granular heat-transfer contact materials tosupply the required heat of reaction. These granular materials areheated to somewhat above the required reaction temperature, and the feedgases, usually preheated to within a few hundred degrees of the requiredreaction temperature, are then contacted directly with the heated solidsfor a controlled period of time, and are then removed and quenched tobelow the decomposition temperature of acetylene. By this procedure,good control of heat transfer, and gas temperature is generallyobtainable. Any coke formed is continuously removed on the contactmaterial. However,.even though these factors are adequately controlled,it is found that low yields of acetylene are still characteristic, andseverely limit the commercial application of such granular contactprocesses. Moreover, even though the coke formed is continuously removedfrom the reaction zone on the contact material, it is necessary toperiodically or continuously remove the coke from the contact material,usually by combustion, in order to prevent excessive build-up in thesize of such particles.

Most of the previously proposed methods employing granular heat-transfersolids are of the countercurrent flow type, or embody essentiallystationary beds of contact material, as for example fluidized beds. Insuch processes, the maximum permissible gas velocity is limited 7 by thelifting velocity of the solids. This severely limits the volume capacityof the apparatus employed. Since the gas velocity is thus limited, andthe contact time must be of a very low order, these processes to beeffective at all, must. also be limited to the use of relatively shallowbeds of contact material. This limitation leads to other diificultiessuch as channeling of gases in the contact bed, and uneven contact timesand gas temperatures" 'through different parts of the bed. .The presentICQ 1 2 process avoids these difficulties by providing for concurrentflow of gases and solids.

It is therefore a broad object of this invention to provide economicallyfeasible methods for the manufacture of acetylene by thermal cracking ofhydrocarbon gases.

A further object is to provide suitable modifications in the processesemploying particle-form solid heat transfer contact materials wherebythe acetylene yields are increased, and coking is minimized.

A specific object of the invention is to provide an optimum relationbetween reaction gas velocities and solid contact velocities whereby thelaydown of coke on the contact material is minimized and maximum yieldsare obtained.

A further object is to avoid the limitations as to gas flow velocityinherent in previous countercurrent gassolids flow processes orfluidized bed processes, wherein the maximum gas velocity is limited bythe lifting velocity of the solids.

A further specific object is to reduce the expense involved in excessivedecoking operations on the contact material.

.Still another object is to provide adequate means for controlling andlimiting the reaction period of gaseous reactants at high temperatures;

Other objects of the invention will be apparent to those skilled-in theart from the more detailed description which follows.

I The feed materials employed herein consist predomi nantly of the lowerhydrocarbon gases'such as methane, ethane, propane, butane, ethylene,propylene, and mixtures thereof such as natural gas. Higher hydrocarbonsmay also be employed. The temperatures employed may range between about1800 F. and 3000 F. However, acetylene is not stable at suchtemperatures, and overheating results in the decomposition thereof toform coke. It is therefore also necessary to limit the period of timeduring which the gases are held at high temperatures to a maximum ofabout 0.5 second. Even shorter reaction periods are desirable, and mayrange downwardly as low as 0.001 second. 1 The preferred reaction periodis between about 0.005 and 0.1 second. The formation of acetylene inpreference to coke is likewise favored by low pressures, preferably fromabout /2 to 1 atmosphere. Higher pressures result in greatercokeformation. The overall requirements for the desired reaction thereforemust embody methods for obtaining high temperatures for a short periodof time at low pressures.

The prior art procedures employing heated pebbles or other particles asthe heat transfer medium have been found to result in substantiallylower yields of acetylene than may be obtained by employing a furnaceheated tubular reactor. However, as stated above, such exteror reaction.

nally heated tubular reactors rapidly become plugged with carbon andrequire periodic shutdowns for carbon removal. It has now been found,however, that the yields of acetylene obtainable by contact of the abovenot known with any great degree of certainty, but several theoreticalexplanations are possible.

One such explanation may be that gas flow which is obstructed by-solideddying, or mixing of gas increments at different stages The acetyleneprecursors first formed in obstacles results in an undesirable thegas-flow front which are at a high energy level may be diverted from thedesired combination with other such particles to form acetylene, and maycombine to a larger xtent wi h part cles or ons at a lower nerg l v l tform coke for example. Qther theories are possible, but n th absence ofxp r mental orrob r ion, h re ult obtained h re n u t be reg r ed as pre y emp al The most practic l me h d f r r uc ng th rel i e l c ti s Esas and-soli is t p o de hat amoun essentially toccnc rr nt fl w oi bothm t ri l h gh the reaction zone. This may be accomplished by passing thefeed gases horizontally, downwardly, or upwardly h u h the reaction zont g er ith the desire mo nt f preheated g nul r s d.- Ih heated solids epref rab y introduced nto the gas tream at one or mor points byaspira cso by sui a e metering devices, such as will be described hereinafter. Inall cases, however, the olids an gase 'ilow oncurrently at approximatelythe same velocity, and, alter the desired reaction period, h g e mcooled r pi ly, a by an fer or steam quenching.

It is ordinarily preferable to separate the reaction gases iii m thesolids before quenching in order :to avoid reducing the tcmperatureofthe solids, which will thus require less reheating for the next reactioncycle. Howet en'the,

combined solids-gas suspension may be quenched if desired, especially ifthe heat removed from. the solids can be utilized to advantage for otherpurposes.

in a preferred modification of the invention, the ratio of solids tofeed gas in the reactor is maintained at less than about it) pounds per5. c. f. in order to reduce the solids handling cost to a minimum. lnoperating according to this modification it, is usually necessary toheat the solids to a higher temperature in order to provide thenecessary heat balance, e. g., to'bctween about 2500- 3200 F. With theusual feedgases, and with contact materials in the p cific heat range ofcoke or sillimanite, and with initial temperature differentials betweenfeed gas and contact material of about 500-1000" F., the optimum ratioof contact material to feed gas lies in the range from about 0.5 to 5.0lbs/s. c. f.

It may also be desirable in some cases to introduce a steam diluent withthe feed gases in order to obtain the desired partial pressure ofhydrocarbons.

T he granular contact materials employed herein may consist of any inertheat-resistant materialQ Examples of such materials include pumice,firebrick, porous ceramic particles, Carborundum, aluminum oxide,calcium oxide, magnesium oxide, spent catalyst granules, petroleum coke,Alundum, Koppers coke, or any other granular material which willwithstand temperatures up to '3000'F.

Cokes are preferred materials inmost cases since they are economicaland, in this process, seldom require regeneration. inasmuch as thebuild-up in particle size due to coke deposition is compensated for byattrition against the walls of the reaction and recirculation vessels.Cokes are. likewise preferable from the standpoint of chemicalinertness.

The particle size may vary considerably. The practical limits liebetween about and mesh. Particles larger than about 10 mesh are found tobe highly ,su's

ceptib'le to spalling and cracking as a result of difierential expansionbrought about by alternating temperature On the other hand, particlessmaller than about 40 mesh are dis-advantageous from the standpointfluctuations.

of ease of separation from the gases. Since it ispreferred to separatethe solids prior to quenching of the reaction gases. and at the sametime it is nccessary'to limit the reaction time to a very short period,the gases must be rapidly separated from the solids. than about 40 meshare employed, it is very difficult to separate them before theexpiration of the allotted reaction period by any of the conventionalmethods.

in order to maintain the gases and solids at asncarly he ame elocity asPossible during thereaction period,

if particles smaller it is preferred to employ a reactor wherein theflow is either horizontal or downward, or at some angle, between thesetwo extremes. The reason for this preferonce may be understood byconsidering the mechanics involved. In employing a downfiow reactor, thesolids, starting from their initial velocity V0, will rapidly be broughtto the gas velocity Vg by frictional gas drag plus the acceleration ofgravity. After reaching the-gas velocity, the solids will continue toaccelerate by gravity until their terminal velocity V; is reached. Thisterminal" velocity will be equal to the gas velocity, V; plus thesettling velocity V5 of the particular solids in the particular gas. Inother words: 1

In the case of an upflow reactor, the solids, starting from V0, willreach a terminal velocity which is equal to the gas velocity minus thesettling velocity,"'or-r ll Vt: Vg

In this case also the solids velocity at any point between V0 and Vtwill be closer to than in an upfiow jreactor In the case of a horizontalreactor, Vt is clOsiftoW/IQ:

than in either an upfiow or downfiow reactor. However the terminalvelocities are not ordinarily reached herein." prior to the expirationof the reactionpcri'od due itoihc'l relationship existing betweenparticle size, particle density and gas density. It is thereforepreferable to employ, as

a practical matter, either a downflow or a horizontt reactor, or oneinclined to some angle between these, I, extremes in order that thesolids velocity will be as close;

to Vg as possible during thereaction period. In all cases; it ispreferable to adjust the particle'size andi/Qt spccifi' gravity, and/ orthe gas flow direction so thatthe rel e difference between gas andsolids velocity 'duriiigQthe," reaction period'will not be more thanabout 20 feet'pe'r second.

The invention may perhaps be most readily undemimdl by referring to thedrawing attached hereto, WifliQhl5. partly elevational and partlysectional view of .a..,speciiic; type of apparatus for carrying out the,inventioj l Referring more particularly to the figure, .h' apparatusigrepresents a suitable downfiow typeofrcactolt Ihsl QEtl gas, which ispreferably preheated to bitty/coda I 700-4400 F. in a heat exchanger 1,enterskh rgugh tubular conduit 2, the lower end of which isencl "ed theupper portion of a larger tubular reactor "3 R actor 3 may beconstructed of Carborundum, ceramic,

othcr heat resistant material, and may vary in 'iiSld diameter fromabout /2 inch to 8 inches, although other im nsions may be employed. Thelower end ofconduit 2 terminates below or in the vicinity of a-pluralit'y-'of orifices 4, arranged circumferentially in the upperwallof reactor 3. Orifices 4 comrnunicatewith the intcrior j f a urroundingh pper 5 whi h isfimeintained par -i 11?- filled with hot contactmaterial, to a levelaboyeihati of the orifice Th s level is maintainedbygtavilyflwl of solids from a heating system described hereinaiten. Thetemperature of the solids in hopper 5 may yary bfirz; tween about2000-3000" F. The diamotersg f. orifices; 4 should be at least severaltimes that of i fi; contact particles. An orifice plate 6 in conduit lfis arranged ,to actuate a flow control mechanism 7 which in turn upcrates valve 8 in line 9. Line 9 carries st e or the inert gas, undermoderate pressure, e. g. l -'l into hopper 5. By the operation ofcontrol l -a variable steam pressure is maintained about 3000 which isdirectly proportional to the flow rate of feed gas. The variable steampressure in hopper 5 in turn forces a variable quantity solids throughorifices 4 into reactor tube 3 where they fall and mingle with the feedgases. In this manner, the ratio of solids to feed gas may be maintainedat any desired constant level, which may vary between about 0.5-5.0pounds per s. c. f. of feed gas, depending upon the temperature of thesolid material and its specific heat, and the initial temperature of thefeed gas.

After passing into the reaction tube 3, the feed gas is rapidly broughtto a reaction temperature of between about l800-3000 F. by heat transferfrom the suspended solids. This gas temperature should be maintained fornot more than about 0.5 second, and preferably less than about 0.01second, and should then be rapidly quenched to less than about 1400 F.In the modification herein illustrated, the solids are separated fromthe gases prior to quenching in order to avoid lowering the solidstemperature. Gas-solids separation is accomplished in separator whichconsists of a chamber 11 and a concentrically enclosed, enlargedexpansion tube 12, open at its lower end. The gases and solids passdownwardly from reactor 3 into and through expansion tube 12 intochamber 11. The gases are decelerated in chamber 11 to the point wherethe solids settle by gravity to the bottom thereof. Product gases passout through line 14 into a quenching chamber 15. Steam, water or otherinert cooling medium is injected into quenching chamber 15 through line16, and the reaction gases are thereby rapidly quenched to below about1400 F. The cooled gases then pass out through line 17 to gas separationapparatus not shown.

In order to maintain the desired extremely short reaction period ofbetween about 0.5 and 0.005 second,

any one or more process or apparatus variables may be adjusted. The meanpath of the reaction gases between a point A in reaction tube 3 at whichthe desired reaction temperature is reached, and the quenching chamber15 may be shortened or lengthened, or the gas velocity may be increasedor decreased. For example, if a slow gas velocity of say less than 50feet per second is maintained, the gas path distance between point A andthe quenching chamber 15 may be shortened to about 0.25 to 5 feet. Ifhigh gas velocities are maintained, as for example between 50500ft./sec., the length of the hot gas path may be increased to about .2 to100 feet. Conversely, with a constant gas path length, the gas velocitymay be varied to obtain the desired reaction period by varying the rateof feed.

The separator 10 may be replaced by any other known type of gas-solidsseparator, as for example, a conventional cyclone type. In employing acyclone separator the quench gas such as steam may be introduceddirectly into the vortex of the outgoing gases.

The solids which settle in chamber 11 are ordinarily somewhat belowthe-reaction temperature, for example, about 1400-1700" F. and are thentransferred to an induction zone 19. The transfer is accomplished inknown manner by means of gravity flow through downcomers 20, valve 21operated by a solids level control device 22, and conduit 23. A seal maybe provided by introducing steam into the bottom of chamber 11 throughline 18 in order to prevent leakage of product gases into induction zone19.

Induction zone 19 consists of an enclosed chamber 24 housing the lowerend of a lift line 25 which extends almost to the top of a solidssupporting tray 26 having a central downcomer 27 communicating with alower gas chamber 28. An inlet line 29 is provided for entry of hot fluegas from furnace 30. Low pressure hot flue gas is admitted to chamber 28and passes upwardly through downcomer 27 and into lift line 25. Chamber24, and lift line 25 are preferably constructed of heat resistantceramics capable of withstanding temperatures up to F. The solids inchamber 24 flow by gravity into the path of flue gas entering lineZSand-areconveyed upwardly thereby in fluid suspension- The distancebetween the lower end of lift line 25 andtray 26 is adjusted to providethe desired rate of flow of, solids. The temperature of the flue gas issuflicientto reheat the solids to above the desired reaction temperatureduring the lift period.

At the top of lift line 25 the gas-solids suspension. is decelerated inseparator 31 to permit separation of gases from solids. Upondeceleration of gases the hot solids settle on supporting tray 32, andflow by gravity through downcomers 33 into solids reservoir 34. Partlycooled flue gas is withdrawn from space 35 through either or. both oflines 36 and 37, depending upon the position, of valves 38 and 39. Byopening valve 38 and closing, valve 39, the flue gas may be passedthrough heat exchanger to preheat the feed gas. By opening valve. 39 andclosing valve 38 it may be passed through line 37 and into line 29 todilute the hot flue gases. This latter arrangement is employed in orderto obtain any desired ratio between gas velocity and temperature in thelift line. Alternatively, part or all of the spent flue gases may bediverted from line 37 to line 37a and passed through heat exchanger 12ato preheat air for furnace 30. After passing through downcomers 33 thehot solids accumulate in the bottom portion of chamber 34. Fromv thischamber the solids flow through conduit 40 into hop-. per 5 by compactgravity flow. A valve 41v interposed in conduit 40 may be employed toregulate the flow of solids and to prevent back flow of steam fromchamber 5. The lower opening of conduit 40 is positioned in hopper 5 sothat the solids will seek a level above the orifices 4. In the apparatusillustrated, it should be understood that the portions thereof whichshould withstand high temperatures, as for example, the reactor tube andthe various conduits and chambers for handling the heated solids shouldbe constructed of heat resistant materials such as ceramics, Carborundumor firebrick, or in some cases heat resistant alloys may be employed.Also, it will be under-. stood that all parts of the apparatusillustrated should be adequately insulated against heat loss. I

Auxiliary solids injection devices may be employed for introducingadditional solids into one or more sections of the reactor tube 3 inorder to obtain a desired temperature profile. After several cycles ofoperation as described, the particle size of the contact material maybecome substantially increased as a result of coke laydown. The totalvolume of solids will also increase. If the contactmaterial is coke,this increase in particle size and total,

solids volume may be controlled by continuously drawing,

off a side-stream of solids from chamber 11, dividing the side streaminto two portions, A and B, regrinding portion- A to the desiredparticle size and returning it to the solids stream in the reactor anddiscarding, or otherwise utilizing portion B. By varying the volumes ofportions A and B,- adequate control of particle size and total solidsvolume may be maintained. Alternatively, with any type of contactmaterial, these two factors may be controlled by admitting a measuredquantity of air into the flue gases employed for reheating the solids.In this manner the excess coke may be removed by combustion with theflue gases.

Many other variations could be made in the type of apparatus employedfor carrying out this process, and the process should therefore not beconsidered as being limited to the particular apparatus disclosed in thedrawings.

The following examples are cited as operable procedures which may beemployed in practicing this invention, but should not be considered aslimiting in scope.

Example it heated to about 1200 and passed at the rate of about j l0,600.s. c. f./hr. through reactor, 4 inches in inside a refractory tubulardownflow;

diameter, similar, to that shown;

in the figure. Heated coke particles of about 20 mesh are metered'intothe incoming gas stream at the rate of about 3.5 pounds per 5. c. f. offeed gas. The tempera ture of the coke is about 3000 F. A fluidsuspension is formed which flows downwardly at an initial velocityof'about 125 ft./sec. The lower end'of the reaction tube terminates in agas-solids separator 10 as shown in Fig. 1. Ga'sand solids are separatedin separator 10 as previously described, and the hot product gases passimmediately into steam quenching zone 15. The mean gas path between thepoint at which feed gases and solids are first mixed, and the quenchzone 15 is about ft. This distance provides a reaction period at2000-2500 F. of about 0.01 see, at this particular gas-flow rate. Thegases are quenched with steam in chamber 15 to below about 1200*"1. Theproduct gases from this single-pass example are found to contain about8.3 volume per cent of acetylene.

The solids collecting in the bottom of separator are at about 2200 F.,and are then transferred to induction zone 19, as previously described.In order to reheat the solids, hot flue gas from furnace 30 is admittedto chamber 28flunder a low pressure of about 1 p. s. i. g. The distancebetween the lower end of lift line 25 and supporting tray 26 isadjustedto permit the solids to flow into the gas stream at about 37,000 lbs/hr.The ratio of flue gas to solids is' about 2 s. c. f. per pound. Intraversing the lift linthesolids are reheated to 3,000 F.

Example II in order to evaluate the results obtainable by this process,and compare them with those obtainable with stationary contact beds, aseries of experiments was carried out asfollows:

"A. A stream of natural gas at atmospheric pressure, and preheated to1400 F., was passed through a horizontal tubular reactor packed with20-40 mesh coke par-,

ticles in'a stationary bed and heated externally by means of anele'ctricfurnace to amaximum temperature of about 2800 F. The velocity of gasflow was about 400 feet per second and the contact time between2000-2600" F. was about 0.01 second. After running the gases for-30seconds, the reactor became almost completely plugged with carbon sothat no further gas could be passed through. The product gases werecollected and found to contain 2.2% acetylene by volume.

"B. Under exactly similar conditions, but employing an empty tubularreactor, and aspirating the coke particles into the feed gas, wherebythe gas-solid suspension was carried concurrently through the heatedtube, the product gases were found to contain 4.2% of acetylene byvolume.

C. By repeating Example li-B employing 20-45 mesh sillimanite particlesinstead of coke, an acetylene yield of 5.06% was obtained.

These experiments clearly indicate that the tortuous flow of'feed gasesin and around a stationary particle-form contact mass'is disadvantageousfrom the standpoint of acetylene yield and coke production. The evidenceindicates that such a procedure favors the breakdown of acetylene tocoke. By contrast, flowing the gases concurrently with the solids insuch manner as to minimize the relative gasasolids velocity, and therebyreduce the frictional contact of gases with hot solids, results ingreatly improved yields of acetylene, amounting to over 100%, in somecases, of that obtainable with a stationary contact bed. Obviously, acountercurrently flowing bed of contact material would be even moredisadvantageous than a stationary bed, other factors being equal.

While the above description has been limited to the production ofacetylene, the process may be easily modified to'obtain otherunsaturated hydrocarbons, such for example as butadiene, ethylene,acetylene homologs, etc. from the same type of feed gases. For theseproducts it is preferable to employ temperatures within the range of'about '1200 -l400 and contact times of about 1-3 secondsormore.

The foregoing disclosure of this invention is'not to be considered aslimiting since many variations may be made by those skilled in -the artwithout departing from the scope or spirit of the following claims. I

I claim:

1. A continuous process for the manufacture of acetylone which comprisespreheating a stream of gaseous hy-' drocarbon to between about 700 F.and 1400 F., admixing therewith an inert particle-form heat-transfermaterial of between about 10 and 40 mesh preheated to aboveabout 2000 F.thereby forming a solids-gas fluid suspension containing not more thanabout 10 pounds of solids per s. c. f. of gas, passing said fluidsuspension downwardly from horizontal through a non-externally heatedreaction zone at a velocity between about 25 and 400 feet per second,thereby maintaining the relative linear velocity oi said solids and saidgas at less than about 20 feetper second until said gaseous hydrocarbonhas been heated to between 1800-3000 F. for between about 0,005-0.l

second, separating reaction gases from said heat-transfer material, henr pid quench g d eac ases t below about 1400 F. recovering acetylenefrom said reaction gases, reheating said heat-transfer material to aboveabout 2000 F., and recycling said reheated hejattransfer material with afresh charge of said preheated gaseous hydrocarbon. 1

A P c s r ing t cla m 1 w r n said gas ous hydrocarbon comprises a loweraliphatic hydrocarbon.

3. A process according to claim 1 wherein said heat fer ma r al is enial y c ke part cle 4. A process according to claim 1 wherein the flowof said fluid suspension in said reaction zone is substantially r al yownwardv5. A process for the manufacture of acetylene which comprisespreheating a gaseous hydrocarbon feed to bew n ab ut F- and 1400? F.,passing a stream of said preheated feed gas imbibe upper portion of adownflow tubular reactor, admitting inert solid particle-form eatnsfermat r al of b tween a out 10 and 40 mesh preheated to above .2000 F.intosaid feed gas stream by a means responsive t9 he flow rate of saidteed gas thereby forming a downflowing solids-gas fluid suspension con.-

taining not more than about 10 pounds ofvsolid s 9Q! standard cubic footof feed gas wherein the average relative linear velocity of said solidsand said gas is less than about 20 feet per second, allowing said fluidsuspension to flow downwardly until said feed gas has been heated.

to between about 1.800" F. and 300051 for a period or" time betweenabout 0.005 second and 0.1 second, separating reaction gas s from saidhea -tran f materials in a separation zone, rapidly cooling said gaseousproducts to below about 1400" F., passing solids'from said separationzone downwardly to an induc ion zon Pa s ng ho flue gases into saidinduction zone and upwardly therefrom into a communicating gas liftline, entraining said solids into said flue gas steam th eby simu a ouslreheating and lifting said solids to an upper separation Zone, removingspent flue gases from said upper separation 2.011% flowing separatedreheated solids from said upper separation zone into a reservoir, andremixing said solids in said reservoir with fresh feed gas. 1

.6. A process according to claim 5 wherein said heat ranster materialis, esse a ly sols: particles.

7. In a process for the manufacture of acetylene by the pyroly is fhydroc rbons wherein a g o y oa is heated at a high temperature for ashort period of time by contact with inert, preheated, granular solids,the im-' provement which comprises employing therein granular heatingsolids of between about 10 and 40 meshparticle size, dispersing saidsolids into a stream of saidgaseous hydrocarbon at a rate correspondingto not more than about 10 pounds of solids per s. c. f. of gaseoushydrocarbon, and immediately thereafter flowing the resulting gassolidssuspension downwardly from horizontal through a confined reaction zone,continuing said downward flow for a period of time suificient tomaintain said gaseous hydrocarbons at a temperature between 1800 and3000 F. for a reaction period betxveen about 0.001 and 0.5 second, andmaintaining the average relative linear velocity of said solids and saidgaseous hydrocarbon at less than about 20 feet per second throughoutsaid reaction period, and immediately thereafter cooling the resultinggases to below about 1400 F. and recovering acetylene therefrom.

8. A process as defined in claim 7 wherein said downward flow issubstantially vertically downward.

9. A process as defined in claim 7 wherein gaseous product is separatedfrom said solids immediately after said reaction period, and theseparated gases are then cooled to below about 1400 F.

10. In a process for the manufacture of low molecular weight unsaturatedhydrocarbons by the pyrolysis of hydrocarbons wherein hot, inert,granular solids are con tacted with a gaseous hydrocarbon therebyheating saidgaseous hydrocarbon to a temperature between 1200 F. and3000 F. for a reaction period of between 0.001 and 3.0 seconds, theimprovement which comprises limiting the particle size of said granularsolids to between about 10 and 40 mesh, and flowing said solidsconcurrently as a fluid suspension in said gaseous hydrocarbondownwardly from horizontal through a confined reaction zone, said fluidsuspension containing not more than about 10 pounds of said solids pers. c. f. of said gaseous hydrocarbon, and maintaining the averagerelative linear velocity of said solids and 'said gaseous hydrocarbon atless than about 20 feet per second through said reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS2,405,395 Bahlke et a1. Aug. 6, 1946 2,420,558 Munday May 13, 19472,422,501 Roetheli June 17, 1947 2,443,714 Arveson June 22, 19482,471,104 Gohr May 24, 1949 2,548,286 Bergstrom Apr. 10, 1951 2,585,984Alexander et a] Feb; 19, 1952

1. A CONTINUOUS PROCESS FOR THE MANUFACTURE OF ACETYLENE WHICH COMPRISESPREHEATING A STREAM OF GASEOUS HYDROCARBON TO BETWEEN ABOUT 700* F. AND1400* F., ADMIXING THEREWITH AN INERT PARTICLE-FORM HEAT-TRANSFERMATERIAL OF BETWEEN ABOUT 10 AND 40 MESH PREHEATED TO ABOVE ABOUT 2000*F. THEREBY FORMING A SOLIDS-GAS FLUID SUSPENSION CONTAINING NOT MORETHAN ABOUT 10 POUNDS OF SOLIDS PERS. C. F. OF GAS, PASSING SAID FLUIDSUSPENSION DOWNWARDLY FROM HORIZONTAL THROUGH A NON-EXTERNALLY HEATEDREACTION ZONE AT A VELOCITY BETWEEN ABOUT 25 AND 400 FEET PER SECOND,THEREBY MAINTAINING THE RELATIVE LINEAR VELOCITY OF SAID SOLIDS AND SAIDGAS AT LESS THAN ABOUT 20 FEET PER SECOND UNTIL SAID GASEOUS HYDROCARBONHAS BEEN HEATED TO BETWEEN 1800-3000* F. FOR BETWEEN ABOUT 0.005-0.1SECOND, SEPARATING REACTION GASES FROM SAID HEAT-TRANSFER MATERIAL, THENRAPIDLY QUENCHING SAID REACTION GASES TO BELOW ABOUT 1400* F. RECOVERINGACETYLENE FROM SAID REACTION GASES, REHEATING SAID HEAT-TRANSFERMATERIAL TO ABOVE ABOUT 2000* F., AND RECYCLING SAID REHEATEDHEATTRANSFER MATERIAL WITH A FRESH CHARGE OF SAID PREHEATED GASEOUSHYDROCARBON.